198 lines
7.1 KiB
C
198 lines
7.1 KiB
C
/*-
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* Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _SYS_RWLOCK_H_
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#define _SYS_RWLOCK_H_
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#include <sys/_lock.h>
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#include <sys/_rwlock.h>
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#ifdef _KERNEL
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#include <sys/pcpu.h>
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#include <machine/atomic.h>
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#endif
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/*
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* The rw_lock field consists of several fields. The low bit indicates
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* if the lock is locked with a read (shared) or write (exclusive) lock.
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* A value of 0 indicates a write lock, and a value of 1 indicates a read
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* lock. Bit 1 is a boolean indicating if there are any threads waiting
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* for a read lock. Bit 2 is a boolean indicating if there are any threads
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* waiting for a write lock. The rest of the variable's definition is
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* dependent on the value of the first bit. For a write lock, it is a
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* pointer to the thread holding the lock, similar to the mtx_lock field of
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* mutexes. For read locks, it is a count of read locks that are held.
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*
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* When the lock is not locked by any thread, it is encoded as a read lock
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* with zero waiters.
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*
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* A note about memory barriers. Write locks need to use the same memory
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* barriers as mutexes: _acq when acquiring a write lock and _rel when
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* releasing a write lock. Read locks also need to use an _acq barrier when
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* acquiring a read lock. However, since read locks do not update any
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* locked data (modulo bugs of course), no memory barrier is needed to when
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* releasing a read lock.
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*/
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#define RW_LOCK_READ 0x01
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#define RW_LOCK_READ_WAITERS 0x02
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#define RW_LOCK_WRITE_WAITERS 0x04
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#define RW_LOCK_FLAGMASK \
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(RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
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#define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
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#define RW_READERS_SHIFT 3
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#define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
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#define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
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#define RW_ONE_READER (1 << RW_READERS_SHIFT)
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#define RW_UNLOCKED RW_READERS_LOCK(0)
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#ifdef _KERNEL
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/* Very simple operations on rw_lock. */
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/* Try to obtain a write lock once. */
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#define _rw_write_lock(rw, tid) \
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atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
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/* Release a write lock quickly if there are no waiters. */
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#define _rw_write_unlock(rw, tid) \
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atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
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/*
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* Full lock operations that are suitable to be inlined in non-debug
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* kernels. If the lock cannot be acquired or released trivially then
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* the work is deferred to another function.
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*/
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/* Acquire a write lock. */
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#define __rw_wlock(rw, tid, file, line) do { \
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uintptr_t _tid = (uintptr_t)(tid); \
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\
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if (!_rw_write_lock((rw), _tid)) \
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_rw_wlock_hard((rw), _tid, (file), (line)); \
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} while (0)
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/* Release a write lock. */
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#define __rw_wunlock(rw, tid, file, line) do { \
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uintptr_t _tid = (uintptr_t)(tid); \
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\
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if (!_rw_write_unlock((rw), _tid)) \
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_rw_wunlock_hard((rw), _tid, (file), (line)); \
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} while (0)
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/*
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* Function prototypes. Routines that start with _ are not part of the
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* external API and should not be called directly. Wrapper macros should
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* be used instead.
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*/
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void rw_init(struct rwlock *rw, const char *name);
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void rw_destroy(struct rwlock *rw);
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void rw_sysinit(void *arg);
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void _rw_wlock(struct rwlock *rw, const char *file, int line);
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void _rw_wunlock(struct rwlock *rw, const char *file, int line);
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void _rw_rlock(struct rwlock *rw, const char *file, int line);
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void _rw_runlock(struct rwlock *rw, const char *file, int line);
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void _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
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int line);
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void _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
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int line);
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int _rw_try_upgrade(struct rwlock *rw, const char *file, int line);
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void _rw_downgrade(struct rwlock *rw, const char *file, int line);
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#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
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void _rw_assert(struct rwlock *rw, int what, const char *file, int line);
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#endif
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/*
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* Public interface for lock operations.
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*
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* XXX: Missing try locks.
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*/
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#ifndef LOCK_DEBUG
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#error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
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#endif
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#if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
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#define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
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#define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
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#else
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#define rw_wlock(rw) \
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__rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
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#define rw_wunlock(rw) \
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__rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
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#endif
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#define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
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#define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
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#define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
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#define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
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#define rw_initialized(rw) lock_initalized(&(rw)->rw_object)
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struct rw_args {
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struct rwlock *ra_rw;
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const char *ra_desc;
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};
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#define RW_SYSINIT(name, rw, desc) \
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static struct rw_args name##_args = { \
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(rw), \
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(desc), \
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}; \
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SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
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rw_sysinit, &name##_args); \
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SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
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rw_destroy, (rw))
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/*
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* The INVARIANTS-enabled rw_assert() functionality.
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*
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* The constants need to be defined for INVARIANT_SUPPORT infrastructure
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* support as _rw_assert() itself uses them and the latter implies that
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* _rw_assert() must build.
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*/
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#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
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#define RA_LOCKED LA_LOCKED
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#define RA_RLOCKED LA_SLOCKED
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#define RA_WLOCKED LA_XLOCKED
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#define RA_UNLOCKED LA_UNLOCKED
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#endif
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#ifdef INVARIANTS
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#define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
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#else
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#define rw_assert(rw, what)
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#endif
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#endif /* _KERNEL */
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#endif /* !_SYS_RWLOCK_H_ */
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